1. Field of the Invention
This invention relates to a radio paging receiver which can display received message information with numerals or characters, and more particularly to an index managing method and apparatus for received messages for a radio paging receiver which has a plurality of paging numbers.
2. Description of the Related Art
A conventional radio paging receiver which can display a message indicates, when a simple paging signal is received, by means of the sound of a loudspeaker, a lamp or the like that a call has been received. However, when message information is received, the radio paging receiver together with indicating the reception, displays the received message information with characters such as alphanumeric characters on a liquid crystal display unit (LCD) once and then successively stores and accumulates the message information into a built-in memory so that the message successively stored in the memory may be read out and displayed later with characters such as alphanumeric characters on the LCD in response to an operation of a user.
Further, information services by such radio paging receivers as described above have spread recently, and it has become possible to provide a plurality of N paging numbers to one paging receiver so that a plurality of information services can be received by the one radio paging receiver in such a way that stock price information is received with a certain paging number whereas exchange rate information is received with another paging number. A radio paging receiver having a plurality of call numbers provided thereto in this manner has call numbers different for the individual information services, and when messages are to be displayed, identification information for each call number, for example, 1, 2, 3, . . . , or the like, is displayed for each message.
However, the displaying order of messages relies only upon the time series receiving order of the messages stored in the memory completely irrespective of the types of the information services mentioned above, that is, the call numbers.
Thus, another paging receiver has been disclosed in Japanese Patent Laid-Open Application No. JP4-257127/1992 wherein messages stored in a memory are sorted using identification information corresponding to a call number as a key to produce a directory and, when each message is to be displayed on a display unit, a user will refer to the directory to select the required message so that the selected message is displayed.
In particular, the radio paging receiver of the document mentioned above includes, as shown in FIG. 1, an antenna 1, a radio unit 2 which intermittently performs a receiving operation, a decoder 3 for detecting a paging number destined for the self paging receiver and a message from a received signal, a liquid crystal display unit (LCD) 5 for displaying received messages, an EEPROM 6 in which a plurality of N paging numbers provided as paging numbers to the paging receiver are stored, a RAM 7 into which messages, information types and so forth are stored, a notifying apparatus such as a loudspeaker 10 and a driver 9 for the notifying apparatus, and a microprocessor (MPU) 4 for controlling operation of the components.
An information supplier who tries to send a message to the paging receiver will dial a particular paging number from a push-button telephone set of a public communication network or the like and then transmit message information with a push signal.
The paging signal passes through the public network and a paging center office and is converted into an address signal, which is a receiver identification number in a radio section, by a radio base station. Then, the address signal is modulated into a burst signal for the radio section together with a message signal and transmitted all at once.
Several kinds of standards have been established as the format of burst signals transmitted from each radio base station, and as an example, a signal format of the CCIR Radio Paging Code No. 1 or POCSAG is illustrated in FIG. 2.
Each burst signal includes a preamble of 1.125 seconds and a plurality of succeeding batches each of 1.0625 seconds and is transmitted in a FSK modulated state. Each batch includes 17 code words, and the first code word is a synchronization code word (SC). Each of the remaining 16 code words is composed of a total of 32 bits, the first bit indicating whether or not the code words are address words or message words, 20 bits representing addresses or information, a BCH code of 10 bits for allowing error detection and correction, and the last bit a parity bit. Further, the 16 code words are divided into 8 frames each including 2 code words, and each individual pager is called with a particular one of the 8 frames.
Each paging receiver receiving a radio signal compares, by the decoder 3, the address signal (20 bits) demodulated by the radio unit 2 with N paging numbers (each formed from 20 bits) stored in the EEPROM 6. When the received address signal coincides with one of the paging numbers, the paging receiver sends to the MPU 4 a paging number detection flag signal indicating that the receiver has been called and an identification symbol notifying the CPU which one of the paging numbers set for each receiver the call is for (it is). The identification symbols of the paging numbers are determined for each receiver with an arbitrary number of bits and in an arbitrary order so that N paging numbers provided for each receiver may be distinguished with a number of bits smaller than the paging numbers (each formed from 20 bits), and serve also as identification codes showing by type the information services that can be received by each receiver.
After the decoder 3 sends the paging number detection flag signal and the call number identification symbol to the MPU 4, it performs error correction of the message information data sent successively to the paging number and sends only the information bits, one code word at a time to the MPU 4.
The MPU 4 stores the call number identification symbol sent thereto from the decoder 3 into a memory region of the RAM 7, discriminates whether the code words sent successively from the decoder are message information or a paging code, and if the code words are a paging code, stops reception of data at that time. On the other hand, if the code words are message information, the MPU 4 stores the code words into the memory region of the RAM 7. Then, the MPU 4 converts data, which have been stored in the memory, into messages of character data and stores the messages into a message region in the RAM 7. In this instance, if the message region has a message or messages already stored therein, the MPU 4 performs sorting of the message or messages together with the new message based on the call number identification symbols.
After the receiving processing of the message signal is completed, the MPU 4 drives the notifying unit such as a loudspeaker, a light emitting diode LED or the like by the driver 9 to notify the user carrying the apparatus that a call has been received, and displays the contents of the received message on the liquid crystal display unit LCD 5.
The messages stored in the RAM 7 can be read out and displayed, after each has been displayed once upon reception, at any time in response to an operation of a user.
Next, a method of managing messages, characteristic of the present conventional example, is described.
In the message region of RAM 7, a data region of a length for a fixed number of characters is allotted to each page number as a sector on a one sector-one message basis.
The data processing method is variable by message length, and when a message exceeds the number of characters for one sector, sectors are added one at a time and pointers attached, pointing form the front sector to the next sector.
Pointers showing the address of the head sector of each message are attached for the respective fixed addresses.
A table of pointers for showing the addresses of head sectors is called an index table or a directory and each message is managed by this index table or directory, as shown in FIG. 3, a directory is constituted from pointer (a) pointing the next directory, identification symbol N and pointer (b) pointing to the head sector. When a new message is to be stored, a call number identification symbol n of the directory and a call number identification symbol n' of the new message to be stored are compared with each other beginning at the head of the directory, and the directory of the new message is inserted in front of the message which they coincides with both of them, producing pointers to update the directory.
A desired one of the messages stored in the RAM 7 can be displayed on the LCD at any time by the user calling the directory by an operation of a switch button or the like. The message displayed in this instance is read out from the RAM 7 in accordance with the order sorted with the identification symbols of the paging numbers.
However, while the conventional system described above can classify received messages for individual paging numbers, that is, for individual types of information services, when messages destined for one paging number are received from a plurality of information suppliers of the same category, those messages are still displayed the order of reception. Consequently, the conventional system has a problem in that much time is required to retrieve and display a desired message from an information supplier.